The Claisen rearrangement has found extraordinary utility in synthesis (including the total synthesis of a wide variety of natural products) due the opportunity for direct chirality transfer from a carbon-oxygen bond to a carbon-carbon bond and to the stereocontrol afforded by chair transition states. We have recently discovered a new variant of the Claisen rearrangement which is both stereoselective and rapid, and should have substantial value in natural products synthesis. The process may be illustrated with the simple bromomagnesium alcoholate 2 (racemic), which undergoes rearrangement at room temperature to give a single stercoisomer.